Ryu C Hyun, Mandal Debasree, Ren Hang
Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
Center for Electrochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
ACS Meas Sci Au. 2024 Oct 10;4(6):729-736. doi: 10.1021/acsmeasuresciau.4c00061. eCollection 2024 Dec 18.
The gas-liquid-solid interface plays a crucial role in various electrochemical energy conversion devices, including fuel cells and electrolyzers. Understanding the effect of gas transfer on the electrochemistry at this three-phase interface is a grand challenge. Scanning electrochemical cell microscopy (SECCM) is an emerging technique for mapping the heterogeneity in electrochemical activity; it also inherently features a three-phase boundary at the nanodroplet cell. Herein, we quantitatively analyze the role of the three-phase boundary in SECCM involving gas via finite element simulation. Oxygen reduction reaction is used as an example for reaction with a gas reactant, which shows that interfacial gas transfer can enhance the overall mass transport of reactant, allowing measuring current density of several A/cm. The hydrogen evolution reaction is used as an example for reaction with a gas product, and fast interfacial gas transfer kinetics can significantly reduce the concentration of dissolved gas near the electrode. This helps to measure electrode kinetics at a high current density without the complication of gas bubble formation. The contribution of interfacial gas transfer can be understood by directly comparing its kinetics to the mass transfer coefficient from the solution. Our findings aid the quantitative application of SECCM in studying electrochemical reactions involving gases, establishing a basis for investigating electrochemistry at the three-phase boundary.
气-液-固界面在包括燃料电池和电解槽在内的各种电化学能量转换装置中起着至关重要的作用。了解气体传输对这个三相界面处电化学的影响是一项巨大的挑战。扫描电化学池显微镜（SECCM）是一种用于绘制电化学活性异质性的新兴技术；它在纳米液滴池中还具有三相边界这一固有特征。在此，我们通过有限元模拟定量分析了三相边界在涉及气体的SECCM中的作用。以氧还原反应为例，该反应与气体反应物发生反应，结果表明界面气体传输可增强反应物的整体传质，从而能够测量数A/cm²的电流密度。以析氢反应为例，该反应与气体产物发生反应，快速的界面气体传输动力学可显著降低电极附近溶解气体的浓度。这有助于在高电流密度下测量电极动力学，而不会出现气泡形成的复杂情况。通过直接将其动力学与来自溶液的传质系数进行比较，可以理解界面气体传输的贡献。我们的研究结果有助于SECCM在研究涉及气体的电化学反应中的定量应用，为研究三相边界处的电化学奠定了基础。
